Hi @Guido Jeuken ,
Can you try this?
Send-MailMessage -To $rec -From $smtpFrom -Subject $messageSubject -encoding ASCII -body ($azlog | Out-String) -smtpserver $smtpServer
Reference: https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/out-string
Hope this helps!